Electromagnetic coupling device



1931- A. H. COOPER 1,833,316

ELECTROMAGNETIC COUPLING DEVI CE Filed Feb. 5, 1931 INVENTOR ArthurHenr-g Cooper;

HIS A TTORNE coil 1 which may Patented Nov. 24, 1931 UNITED 3 STATESPATENT OFFICE ARTHUR HENRY COOPER, OF IVER, ENGLAND, ASSIGNOR TO VIO'IORTALKING MACHINE COMPANY, A CORPORATION OF NEW JERSEY ELECTROMAGNETICCOUPLING DEVICE Application filed February 5, 1931,.Seria1 No. 513,759,and. in Great Britain February 4, 1930.

The present invention relates to electromagnetic coupling devices, suchfor example, as are used in radio receivers. More particularly, itrelates to coupling means of the above type for use between the high orradio frequency circuits of receiving apparatus and the like. i

.In a radio receiver employing electromagnetically coupled circuits, thevolume of sound emitted by a loudspeaker or similar device in the outputcircuit of the receiver can be controlled by varying the couplingbetween the circuits, This is usually done by moving an inductance coilin one of the circuitswith respect to a corresponding inductance coil inthe 'other circuit. It is found, however, that as the moving coil isshifted from the position of zero coupling the energy transferredincreases very rapidly at first and more slowly afterwards.

obtain an apparently uniform increase in the output energy, judgedaudibly, it is necessary that this transfer of energy between the orshield which is arranged to have maximum magnetic couplin with themoving coil of the device'when t c said moving coil is near the positioncorresponding to zero coupling between the coils of the device.

The invention will be described by way of example with referenceto theaccompanying drawings, in which Fig. 1 shows an electroma etic couplingdevice of the so-called variometer type, in which the moving coil ismounted within a cylindrical fixed coil and is rotatable about an axiswhich is at right angles both to its own axis of symmetry and the axisof symmetry of the fixed coil, while Fig. 2 shows the invention appliedto an alternative form of device.

Referring to Fig. 1, a moving or rotatable In order tocouipling coilsshould increase slowly at first,

rm part of a circuit carrying energy to be transferred, is arranged torotate inside of a conducting cylinder or shield ring 2 open at bothends, the cylinder being fixed as shown in such a position that its axisof symmetrywill coincide with the axis of symmetry of the moving coil 1when the latter mm a position corresponding to zero coupling between thecoil 1 and a fixed coupling coil or winding 4. This position issubstantially at a right angle to the fixed coil or Winding 4. Thecylinder is suitably perforated to allow the passage through it of thespindle 3 carrying the moving coil. The annular shield member 2 providesa closed loop which links electromagnetically with the moving coil insuch a way as to be effectively 'a short-circuited turn at theneighborhood of zero coupling of the coils and by this means the zero isspread out and the increase of ener y transferred from the moving coilto the 'xed coil 4 is rendered more gradual in the neighborhood of thezero position.

In Fig. 2 is shown the invention as applied to an electromagneticcoupling device of the type in which a moving coil 11 is adapted toswing about an axis 12 so that the angle between the planes of coil. 11and a fixed coil or winding 10 can be varied. In this case the shield 13in the form of a copper ring is situated with its plane at a right angleto the plane of the fixed coil 10 and in such a position that it lies inthe plane of and surrounds the moving coil 11 when the latter is in theposition corresponding to zero coupling between the coils of the device.85

' The invention is not limited to electromag,

netic coupling devices of the type described above but maybe applied toany such device in which the amount of coupling is variable by relativemovement between the coupling coils constituting the device.

Having now particularly described and ascertained the nature of my saidinvention, and in what manner the same is to beperformed, I declare thatwhat I claim is:

1. An electromagnetic coupling device comprising a fixed coil, a secondcoil movable withrespect to the fixed coil to a position of zerocoupling, and a low-resistance shortcircuited shield ring arranged tosurround and provide maximum magnetic coupling with the moving coil whenthe said moving coil is near the position corresponding to zero couplingbetween the moving and the fixed coils of the device.

2. An electromagnetic coupling device mcluding a movable coil, acylindrical fixed 4 coil, said movable coil being rotatable about anaxis which is at right angles both to its own axis of symmetry and tothe axis of symmetry of the fixed coil, and a conducting annular shieldinterposed between said coils, said shield being mounted so that itsaxis of symmetry is substantially at right angles both to the axis ofrotation of the movable coil and the axis of symmetry of the fixed co13. An electromagnetic coupling device including two angularly displacedcoils, one of said coils being movable to swing about an axis such thatthe angle between the two coils is variable to provide a coupling rangeinring arranged to lie in the plane of and surrounding the moving coilwhen the latter is in a posltion corresponding to substantially zero couling between the coils of the device.

4. A igh frequency circuit coupling device including in combination, apair of electromagnetically coupled coils, a conducting shieldinterposed between said coils, and means for moving one of said coilswith respect to the shield and the other coil to vary the couplingbetween said coils in a predetermined manner.

5. The combination, in a high frequen circuit coupling device, of a pairof electrically coupled windin means for moving one of said windings toa position coaxial with the other and to another position at an anglethereto, and conducting means arran ed to provide a short-clrcuited ringshie (1 about said movable winding when in said last named position. i

In testimony whereof, I have hereunto subscribilaggxjny name thistwentieth day of J anuary,

ARTHUR HENRY COOPER.-

eluding zero coupling, a conducting shield

